﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace text
{
    class Program
        //变量
    {
        static void Main(string[] args)
        {
            const double PI = 3.1415926;

            const Single pp = 3.14F;
            double r = 5;
            double area = PI * r * r;
            Console.WriteLine(area);
            }
            
            }
        }

        



    

